Human behavioral geneticists recently emphasize the importance of environment. After discussing how to deal with the nature/nurture problem in current perspective, the author introduced Plomin  Daniels' (1987) article on "non-shared environment", which has attracted considerable attention lately. The author also discussed Scarr's criticism on Plomin  Daniels' theory, the concept of genotype-environment correlation. The hypothesis that individual differences are considerably affected by genotype under "average expectable environment" was compared with Jensen's threshold theory. Genotype x environment interaction should also be studied 'especially from the educational point of view. The author's "psychological flexible structure model" was introduced as a new perspective on the interface between heredity and environment.